heat rejection process. Alternatively, the first law of thermodynamics can be used to put the efficiency in terms of the heat absorbed and heat rejected, Utilizing that, for the isobaric process, , and for the adiabatic process, , the efficiency can be put in terms of the compression ratio, where is defined to be . Comparing this to the Otto cycle's efficiency graphically, it can be seen that the Otto cycle is more efficient at a given compression ratio. Alternatively, using the relationship given by process 2–3, the efficiency can be put in terms of , the pressure ratio, Cycle diagrams References Thermodynamic cycles Belgian inventions